using System;

using System.Linq;

using System.Collections.Generic;

​

using System.Globalization;

using Newtonsoft.Json;

using Newtonsoft.Json.Converters;

public class Program

{

    public partial class Contact

    {

        [JsonProperty("gender", NullValueHandling = NullValueHandling.Ignore)]

        public string Gender { get; set; }

​

        [JsonProperty("contact")]

        public string ContactContact { get; set; }

​

        [JsonProperty("mail_address", NullValueHandling = NullValueHandling.Ignore)]

        public string MailAddress { get; set; }

​

        [JsonProperty("Name", NullValueHandling = NullValueHandling.Ignore)]

        public string Name { get; set; }

​

        [JsonProperty("address", NullValueHandling = NullValueHandling.Ignore)]

        public string Address { get; set; }

    }

​

    public static void Main()

    {

        string input = @"[{

    ""L1"": null,

    ""L2"": {

        ""Name"": ""XXX"",

        ""contact"": ""xxxxx"",

        ""address"": ""XXXX""

    }

},

{

    ""L3"": {

        ""gender"": ""XXX"",

        ""contact"": ""xxxxx"",

        ""mail_address"": ""XXXX""

    },

    ""L4"": null

}]";

        var result = JsonConvert.DeserializeObject<List<Dictionary<string, Contact>>>(input);

        result[0]["L2"].Dump();

​

        //assuming that key are not the same

        var flatternResult = result.SelectMany(x=>x);

        foreach (var contactInformation in flatternResult) {

            Console.Write($"\n\n{contactInformation.Key}: is null? {contactInformation.Value == null}");            

            Console.WriteLine(""

                +"\n Address         : "+ contactInformation.Value?.Address

                +"\n ContactContact  : "+ contactInformation.Value?.ContactContact

                +"\n Gender          : "+ contactInformation.Value?.Gender

                +"\n MailAddress     : "+ contactInformation.Value?.MailAddress

                +"\n Name            : "+ contactInformation.Value?.Name

            );

​

        }

    }

}